Although it seems like an oxymoron, there really are such things as flightless flies. Most species of flies that are flightless have their wings reduced or narrowed to some extent, while others in the most extreme environmentrs such as subantarctic islands have their wings absent altogether and look a lot like ants.
Emperoptera montgomeryi Evenhuis
The Flightless Flies of Hawaii
Limonia byani Byers
In Hawaii, there are more flightless species of flies than anyqhere else in the world. Hawaii has a total of 11 known flightless flies. Flightlessness in Hawaiian flies occurs in the families Limoniidae (crane-flies) and Dolichopodidae (long-legged flies).
If you have Adobe Acrobat© Reader downloaded and installed in your web browser as a plug-in, you can easily read a recent scientific report on the flightless long-legged flies of Hawaii as a pdf file. Of 5 known species in the endemic Hawaiian genus Emperoptera, only one still is known to survive. This population is known only from the tallest peak on the island of O`ahu, Mt. Ka`ala (4000 ft [1220 m]). It is thought that the other four species of Emperoptera have gone extinct due to the introduction of predaceous ants and the damage to their fragile forest habitat by pigs.